THE ROPE rests limply on the round cafe tabletop in front of a 40ish woman conservatively dressed in a long black skirt and sweater. The rope is tonight's signal. Other nights the signal is a pair of handcuffs.

Vicki, the owner of the rope, is waiting for other South Bay sadomasochists to join her. They meet here in this Mountain View cafe every Thursday to chat about the scene, maybe brandish a sex toy or two and greet the newcomers who are curious about bondage and domination and who learned about the weekly rendezvous on the Internet. The rope is there to clue in the newcomers about where the S&M folks in the cafe are sitting.

People in the S&M scene call these regular public gatherings "munches." Though munches now happen worldwide, they got their start in the early '90s in Palo Alto. A woman who called herself Stella posted a notice on alt.sex.bondage telling others in the Usenet news group that she would be at a Palo Alto hamburger joint that night and inviting others to come. They dubbed the meeting a "Burgermunch."

In the Bay Area, there are now munches in San Francisco, Berkeley, Fremont (Shy Perverts In Fremont, or SPIF) and Mountain View, which has replaced Palo Alto as the north county destination.

"One reason we have munches is so we can meet in a nonplay environment," Vicki explains. "For me, munches started as a place where I could go and see these were OK people."

The Web sites advertising local munches try to make it clear to curious novices that there's no pressure to become an instant leather master. The Mountain View Munch's Web page says, "[A] munch in a public place is a safe, non-threatening way to check out some like-minded people. You can watch us from a distance and not even introduce yourself, if you like."

Tonight, distinguishing the mainstream from the deviants is a challenge, however. In front of the cafe are a dozen leather-clad suburban goth rockers with conspicuous pierces from which they hang personal ornaments. By contrast, the real deviants in the cafe appear reserved. Aside from Vicki's rope, there's no hint that the handful of people chatting a few feet from the espresso-makers are of the hard-core variety.

Joining Vicki are Samantha (or Sam), the housewife married to an engineer. She is dressed in a bright yellow cotton summer dress, There's Debbie, a 24-year-old big-boned gal, and "Alex," a geeky-looking guy with a Star Trek T-shirt who has never participated in S&M activities, but who likes what he has seen on deviant sexual Web sites.

Most of the regular munchers in the South Bay work in high tech, according to Vicki, who herself works as an administrator a high-tech company. Debbie does tech support for an Internet service provider. "Our group has heavy representation in the computer field because most of us discovered munches online," Vicki explains.

Though Thursdays tend to attract fewer munchers than the regular Wednesday meeting, tonight's turnout of four is smaller than usual. The night before, Samantha reports, some 40 sadomasochists showed up to sip lattes and trade stories.

Of course tonight is the final episode of Seinfeld, arguably the mass cultural event of the year. Vicki and Sam admit that a lot of the Thursday regulars could be staying home to watch Seinfeld--circumstantial proof that even perverts are susceptible to mainstream hype.

Vicki, keeping half an eye on the goth rockers out front, stresses the importance of "informed consent between adults." "People need to know what they're getting into," she says. Sam elaborates that some people go so far as to sign contracts defining how far they're willing to go.

One key is agreeing to a "safe word," because in the S&M universe, crying "no" really can mean "keep going." The one being punished--called "the bottom"--must use other words to tell "the top," or slave master, to stop the action. Sam says that the most common safe words are "orange," which means keep going but lighten up, and "red," which means stop it altogether.

"You want it to be a pleasurable experience," Sam says, even if it's painful.

But they're quick to add that it doesn't have to be painful. Bondage and domination don't always involve whips and chains. "A lot of what we do is role-playing," Vicki says, "acting out a scene from a fantasy. ... Scars are optional."

And remember, group members counsel, never use hot beeswax on your slaves--they could end up in the emergency room.